<form method="post" action="/">
	<button id="search_btn"></button>
	<input type="text" placeholder = "Tìm kiếm" id="search" name="search" size="30"/>
</form>
<script type="text/javascript">
   	var show_menu = false;
	$( document ).ready(function() {
		$( "#search_btn" ).click(function() {
			if($( "#search" ).val() == ""){
				$( "#search" ).toggle();
				return false;
			}
		});
	});
</script>